CULTAN Fertilisation Substantially Reduces Nitrate Leaching in Arable Farming

With CULTAN fertilisation, nitrogen is injected into the soil as an ammonium solution. Multi-year trials conducted by Agroscope show that this method reduces nitrogen leaching by an average 38% without negatively affecting yields.

With the CULTAN method (Controlled Uptake Long Term Ammonium Nutrition), nitrogen in the form of an ammonium fertiliser solution is sprayed into the root area of the plants at the beginning of the growing season. Ammonium does not leach to the same extent as nitrate, which is more commonly used in conventional fertilisation.

Agroscope tested the CULTAN method in a 12-year lysimeter experiment and a 3-year field trial. The aim was to determine whether CULTAN could help lower N leaching whilst maintaining field-crop yields under Swiss conditions, compared to the surface application of granulated ammonium nitrate fertiliser.

Lower nitrate leaching with steady yields

The experiments showed that nitrate leaching across all years and crops was on average 38% lower with CULTAN than with conventional surface application of the fertiliser, with no negative impact on yields. CULTAN therefore enables a more efficient use of fertiliser nitrogen and is therefore a suitable supplementary measure, especially for areas where nitrogen leaching into the groundwater needs to be reduced, or where nitrogen fertilisation is limited for other reasons.

Adapting the timing and approach of CULTAN fertilisation to crops, soil and climate

The experiments also showed, however, that the timing and depth of CULTAN fertilisation should be adjusted to crop metabolism and pedoclimatic conditions.  Ammonium deposition in winter wheat, for example, was too quickly exhausted, whilst later use of CULTAN also led to relatively higher yields in oilseed rape and sugar beet crops compared to earlier fertilisation. Further studies are still necessary to determine the optimal CULTAN fertilisation approach for the individual crops and environmental conditions.

An opportunity for the more-sustainable use of nitrogen fertilisers

Besides reduced nitrate leaching, CULTAN fertilisation could have additional economic and ecological benefits:

1. The experiments suggest that, due to its high nitrogen efficiency, CULTAN also delivers reliable yields when lower levels of nitrogen are used.
2. The fertiliser solution for CULTAN can also be made either from recycled ammonium from wastewater, or from slurry and digestate. In Switzerland, several wastewater-treatment plants are already producing a liquid ammonium sulphate fertiliser that is free from heavy metals and other pollutants. In this way, CULTAN could help close the nitrogen cycle.